Tahoe Shark

I'm getting real close to making my mind up on my GTS mods from a previous post.

A couple of questions for those of you that either have, or a very familiar with centrifugal superchargers on 928's. How about Lag, Z, Tim or anyone else. I'm primarily interested in the noise (whine, gear noise, etc) that the 928's make when supercharged. Please tell me the model and brand of supercharger you have experience with. What pulley or trim package is it? Is the air surge audible when the throttle is snapped shut from a boost condition. When cruising under little boost, can you hear the supercharger. Obviously when under significant boost the supercharger will make noise, thats OK.
Any info you can provide will help things along.

Thanks


Tim

Joe Dyer

Hi Tim,

I have the Vortech T-Trim "Racing Only" model. It is noisy but only at idle. Off idle you don't know it's there. Full boost you don't really hear it, only the engine screaming. Off throttle at full boost you barely hear the air surge from the pop-off valve. There is no lag like some turbos.

My understanding is the S-Trim is much more quiet since it has helical gears instead of straight-cut.

Best of luck on your project.

Tahoe Shark

Joe,

Vortech now has an S and and SQ trim that is supposed to be much quieter. Thats funny, I would not have guessed that it gets quieter off idle. I suppose it's good to ask questions when you don't know something. Your installation looks nice and clean.
Do you have a larger photo of your avatar you could post or send to me? Maybe its on a web page.

Thanks

Tim

Blown Beast

The SQ is so quiet that you will not be able to hear it with the hood closed. However you will hear the blow off valve more depending on how much boost you are making. At 8psi you will not even hear it.

Vortech has a new blower out that is a T-trim with the SQ gears. I would love to have one because you get the best of both worlds.

jorj7

Tim,

You could check the photos from 2003 DEVEK Days
( http://sis125.berkeley.edu/928/devek.../ulthm1_96.htm )

I assume it's the same one.

Tahoe Shark

Thanks jorj7,

That looks like it!!!

Tim

Jim bailey - 928 International

Having heard the T trim ....it literally screams BLOWER ! at low engine speeds . Nothing subtle about it . But with 500 plus RWHP it need not be subtle !

Z

I have at least some personal experience with centrifugal installations on 928s with Vortech S-Trim, Vortech T-Trim, Vortech SQ-Trim, Novi 2000, Powerdyne BD-11a, and Powerdyne XB-1a superchargers. The exact level of experience varies from just seeing and hearing some of those installed on a 928, up to installing, riding in, driving, and being part of the dyno tuning and testing on some. The cars that these various experiences were with range from '78 to '93.

I'm assuming you mean who's kit or fabrication of those parts it was. That would include at least seeing or being involved with installation and testing on the Powerdyne BD-11a and Powerdyne XB-1a from 928 Motorsports, the F.A.S.T. kit with S-trim and SQ-trim, a Projekt 928 installation, Tim Murphy's kit with a T-trim and SQ-trim, and at least three do-it-yourself fabrication and installations that I can think of right now, those being with a t-trim, a Novi 2000, and an S-trim.

Yes. The level of sound can vary quite a bit though, depending on the particular installation, blowoff valve used, and boost level. Tim's, Lag's, and one other car have a diffuser on the blowoff valve used which acts as kind of a muffler, and makes a noticible difference in reducing the sound.

That also varies a lot depending on the supercharger model used in the particular installation. You're probably really most likely to notice any nose from the blower at idle and very low speed part throttle. The T-Trim is more noticable than the S-Trim. The SQ-Trim is definitely quieter than either of them, and is really barely noticable. The Powerdyne BD-11a is internally belt driven, and is quieter than the Powerdyne XB-1a. The Novi 2000 has helical cut geas like the Vortech SQ-Trim, so it's pretty quite as well. That's kind of surprising since it's easily the largest capacity blower of the bunch, and can potentially make a lot more power than any of those others. It's also physically larger, so it's going to take some doing to get it to fit the way you probably want it to. In my opinion, none of them are really that loud as to be annoying, like some of the larger ProCharger ones are. In many instances the noise of the exhast is really louder and much more noticable than the supercharger. I don't know what you want for your particular application and planned power level, but of those mentioned, the Vortech SQ-Trim would probably be the one for you if you want quiet. That's the one in Lag's car, and it's very quiet. During normal driving you're really more likely to hear the noise of the tires on the road than the supercharger.

You're really much more likely to hear and notice the exhaust or engine noise than any supercharger noise under full throttle and high boost.

That new T-Trim is also supposed to have a higher maximum impeller RPM capability than the regular T-Trim.

Lagavulin

My car has the Vortech S-Trim SQ (..’super quiet’ I think), and it is super quiet. At idle, one’ll never know a supercharger is installed.

On the other hand, Tim has the Vortech T-Trim, and it is much noisier at idle, and as Joe said, it’s because it has straight-cut gears versus the SQ’s helical-cut gears.

As a side note, the noisier T-Trim is a more aggressive blower which can spin faster and produce more boost than my SQ. Additionally, my SQ is maxed out at 11 psi, and I would have to buy another blower if I wanted more boost, something I won’t do since my engine is still 10:1 compression ratio.

It depends upon the conditions.

If one is squirting through 35mph traffic and hit boost and let off, as the engine enters back into vacuum, the blow-off valve (BOV) will make an audible hiss as it dumps the excess charge since it has nowhere else to go after the throttle slams shut.

After a full throttle run and the throttle slams shut, the BOV dumps charge as before, but it’s not audible due to the greater exhaust and engine ‘symphony’ (..I just love engine noises!).


Well, one is not under boost while at cruise since the engine is in vacuum at that point, and the BOV is dumping the charge as it’s not needed.

While at cruise though, it must be noted that a ‘swishing’ noise is audible since the car is in vacuum and the BOV is dumping the supercharger’s charge. However, to combat that, there are very small industrial mufflers which eliminates all hissing/swishing noises.

But to answer the question I think you’re asking, anytime the engine is under boost, one cannot hear the supercharger at all.


I see that you have a GTS, and with it’s 10.4:1 compression ratio, you can safely run 5-6 psi of intercooled boost which’ll give you 408.4 and 431.3 rwhp respectively. That is a lot of power and you won’t even believe it’s the same car.

Well actually, that’s not exactly true either since while under vacuum, the car will behave as before, but with an extra 20 ft lbs of torque right off the bottom. However, once you nail it, that’s when you’ll wonder why you waited so long to make the change! Well, that’s what I thought at least.


Yep, me too! Even though I wouldn’t run more than 11 psi, maybe that new supercharger would run in a more efficient island providing a cooler charge for the engine.

I were building a new engine though, I would more than likely get the YS-Trim if they made one counter-clockwise:

http://www.vortechsuperchargers.com/...s/ys-trim.html

Talking about new engines, wait ‘til you guys hear what Tim’s cookin’ up! Nothing is set in stone yet, so no details available.

Jim Nowak

I have an ATI Procharger P-1SC and it is very LOUD! It sounds alot like a big B&M blower at idle. Driving down the interstate it makes a very high pitch whistle....very nice but you will not sneak up on anyone with this blower.

Gerry

Jim - could you elaborate a little on your installation? I like the Procharger series and would like to get one soon.

1- What mounting bracket did you use? Fast , Delta-P, or custom made?

2- What size pulley and how much boost is the pulley producing?

3- What type intercooler and make?

4- What is your C/R and yr shark?

5- Any dyno results or problems yet with oil blowby?

6- Any pix?


Thanks Jim

Tim Murphy

Just a few comments:

The Vortech V2-SQ S trim is very quiet at idle and while driving at very low rpm/speed there is a very slight whine that is audible. Unless you knew what to listen for you would most likely not notice. The impeller rpm to produce 8psi is right in the efficiency range for our application. The V2-T trim, as it would be called, would be oversized at this lower rpm and would possibly give you less performance than the S trim. I'm not sure of the availability of the V2-T trim from Vortech. I don't know if it is publicly available or not. I ran the V1-T trim with the straight cut gears and it was very loud at idle and I didn't car for it at all. With the straight cut gears there is a lot of back lash in the gear train and when at idle there is not enough load to keep the gears in contact and they literally rattle at idle. With the helical cut gears that is no longer the case. Bottom line, I wouldn't ever buy a supercharger with straight cut gears.

Blow off valves:
I started off using the small plastic blow off valve made by Bosche and it would cause surging all the time when it was open. I actually ran without it hooked up when I was at 5psi. I went to a larger blow off valve when I turned up the boost to 8psi and you can hear it "whoosh" when it comes off boost. I put an industrial pneumatic muffler on it and the noise was practically gone. Another device that I will be testing will completely take care of the noise associated with the blow off valves and will be part of my supercharger kit. This might take until spring to do the actual installation of this device.

Joe Dyer

Tim, here's a larger picture.

Lagavulin

Sch-wing!!!

Very nice Joe...

How long before your harness, etc, is fixed? What compression ratio are you running?

Joe Dyer

Lagavulin,

I spoke with Susan yesterday. She says we're on schedule to complete the repair before Christmas, which is nice since I'm hosting an autocross at Marina airport (near Monterey) on the 26th.

For those curious, Marc Thomas and I were test driving the car a few days before Sharktoberfest after Marc had installed an engine oil cooler in the nose. I had re-done all tubing from SC to intercooler as the original work was bleeding air at 5psi. We were seeing 8-9 psi on 2nd gear runs on the freeway when the higher fuel pressure pushed an injector out of the fuel rail, causing a small fire. The engine builder failed to install injector clips on all injectors. We got the fire out quickly, but wiring harness, vacuum lines, rear brake line, MAF, etc... are being replaced.

Not sure of exact compression ratio, but cylinders read 170 lbs instead of 210. Can someone do the math?